Load limit control for elevators



Oct. 30, 1956 w. BECK LOAD LIMIT CONTROL FOR ELEvATORs Filed Oct. 3o, 1955 2 Sheets-Sheet l l y Q R) ZQZQz/' 07 OCt. 30, 1956 W, BECK LOAD LIMIT CONTROL FOR ELEVATORS 2 Sheets-Sheet, 2

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Filed Oct. 30, 1953 United States Patent C) LOAD LIMIT CONTROL FOR ELEVATORS Walter Beck, Rock Island, lll., assignor to Montgomery Elevator Company, a corporation of Illinois Application October 30, 1953, Serial No. 389,218

9 Claims. (Cl. 200-85) This invention relates to a load limit control for elevators, and in particular it relates to a control system in which the hitch plate to which the elevator cables are secured is linked to a pair of relatively fixed beams so that increased load on the elevator cage produces lateral movement of the hitch plate which may actuate a desired control switch mechanism.

Elevator load limit controls are provided so that when an elevator cage or car approaches overload conditions a switch is actuated by the increasing weight on the elevator cage which can illuminate a telltale light, or in some other way warn that overload conditions are being approached. Upon further loading a second switch may be actuated which will cut out the operating mechanism until the overload is removed.

One method of actuating the load limit control switches is by making the floor of the elevator cage a scale which in effect weighs the load and when maximum conditions are reached trips the cutout switch. Such a system is somewhat undesirable because the movement of persons in the elevator car may upset the weighing device.

Other systems have employed the deection of the car lifting beam; but this deflection is so slight that it is very diflicult to operate a switch by means of the deflection unless some sort of a motion multiplying device is employed.

Other types of control systems which use the lifting beams in one way or another have been so high that they occupyl too much space above the elevator car where the height of the top of the shaft limited their permissible height.

Furthermore, it is desirable to arrange the controls in such a way that there is no movement of the switch actuating mechanism until a predetermined minimum load has been reached.

In accordance with the present invention the cable hitch plate is secured by means of parallel links to a relatively fixed cross beam so that as load upon the elevator cage increases the hitch plate is moved sideways. An adjustable compression spring bearing against the end of the hitch plate resists its tendency toward sidewise movement, so that there is no movement of the hitch plate until the predetermined thrust of the spring is exceeded. Preferably a motion multiplying mechanism is employed so that only a small movement of the hitch plate will actuate standard control switches which may be mounted on or adjacent the relatively fixed beam.

When mounted upon the elevator itself, as shown in the drawings, the mechanism has the advantage of requiring almost no more space above the elevator cage than is occupied by the lifting beams themselves.

The invention is illustrated in a preferred embodiment in the accompanying drawings in which:

Fig. l is a schematic view of an elevator with the load limit control mechanism of the invention incorporated therein;

2,769,052 Patented Oct. 30, 1.956

Fig. 2 is a plan View of the mechanism to an enlarged scale;

Fig. 3 is a section taken as indicated along the line 3--3 of Fig. 2;

Fig. 4 is a section taken as indicated along the line 4-4 of Fig. 3; and

Fig. 5 is a section taken as indicated along the line 5 5 of Fig. 3.

Referring to the drawings in greater detail, and referring rst to Figs. l and 4, an elevator mechanism includes a pair of lifting beams 9 beneath which is a stile 10 for supporting an elevator cage or car 11. Bolted to the underside of the lifting beams 9 is a pair of frame plates 12, each of which is provided with two depending bearing blocks 13. A hitch plate 14 is mounted between the lifting beams 9 and is provided with two pairs of bearing blocks 15 which, as seen in Fig. 3, offset laterally from the corresponding bearing blocks 13 so that the hitch plate 14 may be linked to the lifting beams 10 by means of two sets of parallel links 16 to form a parallelogram linkage which includes the lifting beam 9, hitch plate 14 and links 16. The hitch plate 14 is apertured to receive cables 17 the lower ends of which are provided with cushioning springs 18 which bear against the underside of the hitch plate 14 in the customary manner. By reason of the parallel links 16, when the load upon the elevator cage 11 is increased the additional weight upon the lifting beams 9, acting through the links 16, tends to move the hitch plate 14 laterally to the right in a translatory manner as seen in the drawings. As best seen in Figs. 2 and 3, a cross bar 19 extends between the frame plates 12 at the left hand end of the hitch plate 14 and is provided with a hardened insert 20 which serves as an abutment stop for the hitch plate, limiting the movement of the plate in one direction. Spaced from the opposite end of the hitch plate 14, and extending between the frame plates 12 in alignment with the hitch plate, is a spring support bar 21 which is centrally apertured to receive a screw 22 the inner end of which carries a spring supporting lug 23 the position of which with respect to the hitch plate 14 may be adjusted by movement of the screw 22. A spring lug 24 is secured to the end of the hitch plate in alignment with the lug 23, and a heavy compression spring 25 is interposed between the spring lugs so as normally to thrust the hitch plate 14 against the abutment stop 19. The thrust of the spring 25 is adjustable by means of the screw 22.

Mounted on one of the frame plates 12 and extending upwardly along the side of one of the lifting beams 9 is a bracket member 26 at the lower end of which is a block 27 for a pivot pin 28 on which is pivotally mounted a bell crank 29 which extends upwardly alongside the bracket 26. The bell crank 29 is normally drawn toward the hitch plate 14 by means of a tension spring 30, one end of said spring being secured to a cotter pin 31 which impales the bell crank 29 and the other end being secured to a spring stud 32 on top of one of the pivot blocks 15 on the hitch plate. At the top of the bell crank 29 is a cross bar 33.

Secured to the top of the bracket 26 is an angle bracket 34 which is lapertured -to receive a set screw 35 by means of which the normal position of the bell crank 29 with respect to the hitch plate 14 may be Iadjustably fixed. Likewise supported in the bracket 34 are a pair of externally threaded sleeves 36 which serve =as mounting members for .a pair of Microswitches 37 lthe plungers 38 of which extend through the sleeves 36 and bear upon the cross bar 33 at the upper end of the bell crank 29. The set screw 3'5 and sleeves 36 are adjusted until lin its nor- 0 mal position the bell crank 29 retains the switches 37 in their desired positions.

Secured rat the lower end of the hitch plate 14 is an angle member E39 which has at its lower end a threaded lug `40 which may be adjusted to bear upon the front of the bell crank 29 when the bell cra-nk is in its normal position. Thus, las soon as the hitch plate 14 is permitted to move to the right lagainst the thrust of the spring 25, the Vlug 40 pressing against ythe bell crank 29 moves the 'bell crank against the Vtension of the spring '30, and permits the plungers 38 of the Microswitches 37 to move to the right, thus `actuating the switches. Ac-tuation of the switches 137 may be employed by meansl of appropriate electric circuits (not shown) to perform .any desired operation in connection with the Iload limit control. Thus, one of the switches 37 might be so set as to be actuated ahead of the other switch, and could light a telltale light or ring a 'bell inthe elevator cage to warn of an approaching overload, while the second switch would open later to lcompletely cut off the operating mechanism in case of absolute overload.

The foregoing detailed description is given for clearness ofV understanding only and no unnecessary limitations are to he understood therefrom, as some modifications will be obvious to those skilled in the tart.

I claim:

l. In an elevator system, load limit control means including: a relatively fixed beam; a hitch plate; cable means secured to the hitch plate; an elevator ca-ge supported by the cable means; mechanica-l means operatively connecting the hitch plate to .the beam so that increased load on the cage tends to produce lateral movement of the hitch plate with respect to the beam; spring means exerting lat-eral thrust upon the hitch plate to resist said lateral movement of the hitch plate; .and switch means adapted to be .actuated in response to lateral movement of the hitch plate.

2. In an elevator system, load limit control means v-inclu-ding: a relatively fixed beam; -a hitch plate; cable means secured to the hitch plate; .an elevator cage supported by the cable means; parallel links connecting the hitch plate to the beam so that increased load on the cage tends to produce translatory later-al movement of said hitch plate with respect to the beam; spring means exerting lateral thrust upon the hitch plate to resist said lateral movement of the hitch plate; and yswitch means adapted to be Iactuated in response to lateral movement fof the hitch plate.

3. `In 'an elevator system, load limit control means including: a relatively fixed beam; a hitch plate; cable means Isecured to the hitch plate; an elevator cage supported by the cable means; mechanical means operatively connecting the hitch plate to the beam so that increased load on the cage tends to produce lateral movement `of the hitch plate with respect to the beam; spring means exerting lateral thrust upon the hitch plate 'to-resist said lateral movement of the hitch plate; switch means; and motion multiplying means openatively connected to the hitch plate for actuating said switch means in response to lateral Inovem'ent of the hitch plate. f

4. In an elevator system, load limit control means including: a lifting beam; an elevator cage suspended beneath the lifting beam; la hitch plate adjacent the lifting beam; cable means secured to the hitch plate; mechanical means operatively connecting the hitch plate to the lifting beam so that increased load on the cage tends to produce lateral movement of the hitch plate with respect to the beam; spring means `exerting lateral thrust upon the hitch plate to resist said lateral movement of the hitch plate; and switch means adapted to be actuated in response to later-al movement of the hitch plate.

5. In an elevator system, load limit control means including: a pair yof spaced, parallel lifting beams; an elevator cage suspended beneath said beams; a hitch plate between the beams; cable means secured to the hitch plate for suspending the plate, lifting beams and elevator cage; parallel links connecting the hitch plate to the lifting beam so that increased load on the cage tends to produce translatory lateral movement of said hitch plate with respect to the beams; spring means exerting lateral thrust upon the hitch plate to resist said lateral movement of the hitch plate; and switch meansV adapted to be actuated in response to lateral movement of the hitch plate.

6. In an elevator system, load limit control means including: a pair of spaced, parallel lifting beams; an e'levator cage suspended beneath the lifting beams; a hitch plate between the lifting beams; cable means secured to the hitch plate for suspending the plate, Alifting beams and elevator cage; parallel links connecting the hitch plate to the lifting beams so that increased load on the cage tends to produce translatory lateral movement of said hitch plate with respect to the lifting beams; spring means resisting said lateral movement of the hitch plate; switch means mounted on the lifting beams; Vand motion multiplying means operatively connected to the hitch plate adapted to actuate said switch means in response to lateral movement of the hitch plate. Y

7. In an elevator system, load limit control means including: a relatively fixed beam; `a hitch plate; cable means secured to the hitch plate; an elevator cage supported by the cable means; mechanical means operatively connecting the hitch plate to the beam so that increased load on the cage tends to produce lateral movement `of the hitch plate with respect to the beam; an adjustable spring `support secured to the beam in laterally spaced yrelationship to the hitch plate; .a compression spring extending between said support and an `end of the hitch plate; land switch means 'adapted to be actuated in response to lateral movement of the hitch palte.

8. In an elevator system, load limi-t control means inclu-ding: a pair of lifting beams; an elevator cage suspended bene-ath said lifting beams; a hitch plate between the lifting beams; cable means secured to the hitch plate Y for suspending the plate, lifting beams and elevator cage; parallel links connecting the hitch plate to the beams so that increased load on the cage tends to produce translatory lateral movement of said hitch plate with respect to the beam; an abutment stop adjacent one end of the hitch plate; :a spring support extending between the beams opposite the other end of the hitch plate; la compression spring extending between the spring support and `an end of the hitch plate to thrust the hitch plate against the abutment stop; switch means on the lifting beam; and motion multiplying means on the hitch plate for Iactuating the switch means in response to the lateral movement of the hitch plate.

9. In an elevator system, load limit control means including: a relatively xed beam; a hitch plate; cable means .secured to the hitch plate and provided with cushioning :springs under the hitch plate; mechanical means pivotally connecting the hitch plate to the beam so that increased load on the cage tends to produce lateral movement of han end'of the hitch plate; independent spring means resisting said lateral movement `of the 'hitch plate; and switch means adapted to be actuated in response to later-al movement of the hitch plate.

References Cited in the le of this patent UNITED STATES PATENTS 823,455 Willcox June 12, 1906 949,266 Davey Feb. l5, 1910 2,173,289 Staley Sept. 19, 1929 2,404,415 Turner July 23, 1946 2,589,329 Borovec c- Mar. 18, 1952 

